High-efficiency synthesis of 5-ethoxymethylfurfural from biomass-derived 5-hydroxymethylfurfural and sugars catalyzed by magnetically recoverable hydrogen sulfate ionic liquid

The conversion of 5-hydroxymethylfurfural (HMF) and carbohydrates to 5-ethoxymethylfurfural (EMF) is an attractive biomass transformation owing to the potential application of the resulting product as a fuel additive. In this work, the imidazolium hydrogen sulfate ionic liquid was grafted on the surface of silica-coated iron oxide magnetic nanoparticles using cyanuric chloride as linker, and such a magnetically separable solid acid catalyst is referred to as HSO4/SMNPs. The catalytic activity of HSO4/SMNPs was evaluated for the etherification of biomass-derived HMF with ethanol and sequential dehydration/etherification of sugars to produce EMF. The impact of various reaction parameters was studied to achieve the optimal yield of EMF. HSO4/SMNPs provided EMF yields of 94.3%, 68.2%, and 53.3% from HMF, fructose, and inulin in ethanol, respectively, without the need for high boiling point co-solvents. Extraordinarily, the catalyst can be readily separated from the reaction mixture by applying a permanent magnet and reused for five times without substantial activity decrease.